Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.42	7.565%	$204.8253	$204.83	$204.85	$204.80
Purchase #2	$147.50	12.858%	$166.4656	$166.47	$166.45	$166.50
Purchase #3	$179.55	9.503%	$196.6126	$196.61	$196.60	$196.60
Purchase #4	$157.29	11.597%	$175.5309	$175.53	$175.55	$175.50
Purchase #5	$215.74	13.314%	$244.4636	$244.46	$244.45	$244.50
Purchase #6	$13.26	12.143%	$14.8702	$14.87	$14.85	$14.90
Purchase #7	$39.97	7.193%	$42.845	$42.85	$42.85	$42.80
7 purchase totals =	$943.73		$1,045.6132	$1,045.62	$1,045.60	$1,045.60